<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>无标题文档</title>
<style>
div{ width:100px;height:100px; background:red; transition:1s;}
div:hover{ width:200px;height:200px; background:blue;}
</style>
</head>
<body>
<div></div>
</body>
</html>
